This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 101 49 969.8-26, filed on Oct. 10, 2001 in the Federal Republic of Germany. The entire disclosure of the German Patent Application is incorporated herein by reference.
The invention relates to a method for controlling the warp shed formation and warp shed closure with the aid of a jacquard that is part of a weaving loom. The weft threads are mechanically inserted into the open warp shed by grippers or so-called rapiers. One rapier is positioned at an entrance to the warp shed, the other rapier is positioned at an exit of the warp thread.
Weaving looms with a mechanical weft thread insertion for producing a fabric having a predetermined fabric pattern are operated in combination with a jacquard which controls the repeated shed formation of the warp threads. One weaving cycle includes an opening of a warp shed, an insertion of a weft thread into the warp shed and closing of the warp shed followed by a beat-up of the inserted weft by the reed against the fabric. A mechanical weft insertion by two grippers or rapiers requires a special attention to the shed formation to avoid damaging the warp threads by the rapiers as the rapiers are moved out of the shed which extends over the weaving width defined between the weft entrance and the weft exit of the warp shed. A jacquard of modern construction comprises a plurality of electrically or electronically controllable warp lifting and lowering components or drives which, for example, are driven by controllable electric motors. Such jacquards do not comprise any knives nor any drives for such knives.
Each warp thread of all warp threads in the loom is guided and driven by the jacquard operating components including harness cords, etc., which lift and lower the respective warp thread through coupling elements which connect the harness cords with respective drives and with heddles and pull back members to move each of the warp threads. Each harness cord and its pull back member are guided and driven by a respective individual operating component or drive motor in such a way that the warp shed is formed by the warp threads. For this purpose one group of warp threads is moved vertically from a first upper position to a second lower position while another group of warp threads is simultaneously vertically moved from the second lower position to the first upper position to thereby form the warp or loom shed. An electronic control or CPU is provided for the controlled motion of the warp threads for the shed formation and respective shed closure. The electronic control drives each of the warp operating components in accordance with a preselected program by transmitting signals from the control unit, for example, to the above mentioned individual electric motors for driving the warp threads.
European Patent Publication EP 0,353,005 B2 (Palmer) discloses an example of a weaving loom with a drive mechanism that performs the function of a jacquard as described above. Each individual warp thread is moved by its heddle and a respective heddle actuator between end positions which are variable in accordance with a fabric pattern representing program stored in the memory of a computer. The operation is such that a preselected pattern is formed in the textile being woven. The control data stored in the computer memory represent selected operating parameters that result in an xe2x80x9coblique or parabolic sheddingxe2x80x9d during the weaving operation.
The disclosure of the European Patent Publication EP 0,353,005 B2 does not provide for different shed formation configurations for different types of looms such as mechanical looms with a weft insertion by two rapiers or fluid jet looms with a fluidic weft insertion by fluid nozzles for transporting a weft thread through the warp or loom shed having an entrance and an exit. Thus, the shedding or the shed motion profiles for the same fabric pattern are identical, namely oblique or parabolic for a loom with mechanical weft insertion and for a loom with pneumatic weft insertion. The use of either oblique or parabolic shedding in any type of loom does not take into account that different types of looms have different shedding requirements for achieving an optimal weaving operation.
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to control the shed motion profile or shedding in accordance with the requirements of a loom with a mechanical weft insertion;
to control the motion of individual heddles in such a way that in a loom with a mechanical weft insertion by grippers or rapiers, the shed motion profile or shedding permits a safe insertion and withdrawal of the grippers or rapiers into and out of the weft insertion channel to thereby reduce damage to the warp threads;
to provide an increased operational life for the components that operate the heddles including the warp pull back elements; and
to reduce the wear and tear on the warp threads and of the heddle operating or heddle driving components and pull back elements to thereby increase the operational life of weaving looms with a mechanical weft insertion while gently handling or driving the warp threads for the shed formation.
The above objects have been achieved according to the invention by a method which takes shedding requirements of a loom with mechanical weft insertion into account for operating the individual heddles in a heald shaft in response to electronic control data or respective signals stored in a computer memory. The data for individually controlling the lifting and lowering of the warp threads take into account a safe timing for the withdrawal of the weft inserting rapiers along a weft entrance section and along a weft exit section of the weaving width of the loom. According to the invention the driving of the individual heddles depends on the instantaneous angular rotational position of a main loom drive shaft in such a manner that a shed stop is assured simultaneously in the weft entrance section of the warp shed being formed and in the weft exit section of such a shed when the maximum shed opening occurs and further so that a shed stop is avoided simultaneously in a weft advance section or at least in a center of the shed between the shed entrance section and the shed exit section. In the entrance and exit sections the shed motion profile has a distinct shed stop between rising and falling curve portions. Preferably, the shed formation or motion profile without a shed stop at least at the shed center in the intermediate section between the entrance and exit sections is so controlled that the shedding motion resembles a sinusoidal curve or profile.
More specifically, according to the present method the following steps are performed:
(a) dividing a given weaving width of the weaving loom into at least three sections including a weft entrance section A0, a weft advance section A1, and a weft exit section A2,
(b) mechanically inserting each weft thread into the warp shed,
(c) generating reference signals based on angular degrees of rotation of a main loom drive shaft in each weaving cycle,
(d) providing separate heddle motion control signals for each of a plurality of individually controllable heddle drives, and
(e) controlling each of the heddle drives by separate heddle motion control signals in response to the reference signals so that in the weft entrance sections A0 and in said weft exit section the warp shed is temporarily stopped when said warp shed is in its maximally open position, and so that simultaneously a shed stop is avoided at least at a center of the weft advance section or in the center of the shed when the shed is maximally open.
The shed formation according to the invention treats each individual warp thread more gently compared to the forces that are applied to the warp threads in a conventional shed formation.
As a result, the invention substantially reduces warp breakage with a corresponding reduction in the interruptions of the weaving process that conventionally occur. Additionally, the operating or drive components for the individual heddles and the heddles themselves including warp thread holders, such as an eye or a hook in each heddle, are also subject to lesser forces as compared to the prior art, thereby reducing wear and tear as well as excess swing motions of the individual warp threads.